1. Field of the invention
The present invention relates to a method and recording and reproducing device for correcting an image signal by bandwidth compression accompanying a DCT (Discrete Cosine Transform) or other block processing method.
2. Prior art
DCT and other conversion coding processes have become the standard in bandwidth compression due to their high efficiency, typically compressing the raw image data from 1/10th to 1/40th of their original size.
An unfortunate side effect of a high compression ratio, however, is the appearance of so-called block distortion resulting from visually obvious level differences between blocks. For example, when the signal is compressed with DCT blocks comprising eight pixels horizontally and vertically, there will be lines in the decoded signal every eight pixels horizontally and vertically, resulting in a picture that is visually disturbing to view.